A large multicenter trial performed by several international brain tumor and radiotherapy groups demonstrated a median survival in patients with newly diagnosed GBM of only 12.1 months with surgery/radiotherapy and 14.6 months when temozolamide therapy was added. This dismal prognosis for patients with malignant gliomas remains despite recent advances in diagnostic and therapeutic techniques. Even with the use of advanced MRI pulse sequences and PET radiopharmaceuticals, the true extent of tumor infiltration into surrounding normal brain is often inadequately characterized prior to surgical resection and radiation treatment. Moreover, following treatment, conventional MRI also has limitations in distinguishing pseudoprogression and treatment necrosis from tumor recurrence which can lead to false positive findings that may subject patients to unnecessary procedures and/or treatments. Clearly, new diagnostic and management strategies are needed for these patients. Our lab is developing radioiodinated NM404 as a diapeutic agent for the detection and treatment of a wide variety of solid tumors, including brain tumors. NM404 is a refined, second-generation, phospholipid ether analog that is characterized by preferential tumor uptake and prolonged tumor retention in 50/52 human xenograft, spontaneous and transgenic preclinical tumor models, including gliomas. The mechanistic basis for the selective uptake of NM404 is due to selective insertion into lipid rafts and resultant internalization into the cell. Malignant cells are now known to have greatly increased amounts of lipid rafts compared to normal cells. When labeled with the therapy isotope iodine-131, NM404, has produced significant prolongation of life following a single injection in a dozen human xenograft tumor models in mice. The goal of this imaging proposal is to first optimize the PET imaging parameters of 124I-NM404 in malignant brain tumor patients and then compare the tumor sensitivity and specificity of this agent with current state-of-the-art MRI imaging techniques and pathology. If NM404 PET/CT results prove superior to MRI in accurately defining the true extent of tumor infiltration, then this new technique may be used to guide preor intra-surgical biopsies, improve surgical and radiotherapy planning, monitor treatment response, and differentiate pseudoprogression or radiation necrosis from true tumor recurrence. This new diagnostic information could help significantly improve patient survival with current therapies. Additionally, if coupled with new 131I-NM404 systemic radiotherapy, patient survival may be dramatically improved.